Commonly, stereo systems have utilized two separate speaker cabinets or enclosures which may typically be spaced 5 to 10 feet apart and which are disposed for radiating more or less directly toward the listener. These types of systems have certain disadvantages associated therewith. For example, the sound appears to come from two distinct sources rather than being spread over an area or volume as would be the case at an actual life performance. Also, because of the relatively large separation between the cabinets or enclosures there is an empty area of sound between the two enclosures. Sometimes, this empty area is filled with an additional third speaker which, however, provides a rather cumbersome array of three separate enclosures.
Because the direct radiating system does not enhance the reverberation often lost in stereo recording, two additional speakers are presently being added to provide a quadraphonic effect.
This now means that there is an even more cumbersome system comprising at least four enclosures. With the direct two speaker system the reverberation is quite unreal as it is coming from only two distinct directions.
Another disadvantage with the direct radiating system employing two enclosures is that the speakers are separated far enough apart so that the bass enhancement is not appreciably provided. The bass enhancement is a function of the mutual coupling between the enclosures which in turn is a function of the distance therebetween. Furthermore, since in these prior art systems the speakers are mounted in the front of the enclosures there is no spacial enhancement from reflections from the rear wall of the listening room.
When the speaker enclosures are located in a room they have images which are at an equal distance on either side of the walls of the room. These images can contribute to the stereo effect. However, with the conventional system wherein the enclosures are separated they are generally close to the sidewalls of the room and consequently the images are also close to the sidewalls. In the present invention the speakers, being close together, provide images that are now far apart and can create a wider panaroma of sound. Alternatively, with the direct radiating speaker system the level of the sound from the images is small in comparison to the direct sound. However, if, with the direct radiating system, the two speakers are placed close together in the center of the room then there is the other disadvantage of not providing a full stereo effect.
The reflecting type system such as shown in U.S. Pat. No. 2,710,662 can overcome some of the disadvantages found in the two speaker direct radiating system. However, other reflecting type systems that exist also have disadvantages.
One system uses two speaker enclosures and directs the sound toward the rear wall of the room. Although the reflecting sound yields an improved stereo effect the center image is the result of the right channel mixing with the left channel resulting in image confusion in the center. Also, with the two separate enclosures little increase in the low frequency response through mutual coupling is realized. Moreover, this system requires two separate enclosures for stereo effect.
Another system of the prior art uses one enclosure with the right and left channels facing directly toward the right and left, respectively. In this system the two channels are connected out of phase to produce a null in the center and thus spread the images from one unitary enclosure. This system suffers in low frequency response because the two woofers are out of phase and have a mutual coupling that actually reduces the radiation rather than increasing the radiation. Moreover, because the radiation is maximum towards the right and left, the direction of the radiation from the images is not favorable for listening at removed distances from the enclosure.
Another system is of the type shown in U.S. Pat. No. 2,710,662. This system is a reflecting type that relies on no direct radiation; and thus the images from the side wall are not masked by the high level of the direct sound. However, this prior art system does not provide for both improved low frequency response and increased stereo separation. In fact, this prior art system teaches the reducing of the coupling between the right and left channels which is contrary to the teachings of the present invention.
Accordingly, one object of the present invention is to provide an improved loudspeaker system for use in a listening room and that provides improved stereo effect with a unitary enclosure. Another object of the present invention is to provide a loudspeaker system that is characterized by improved bass response and a spacial effect.
A further object of the present invention is to provide a loudspeaker system that can be embodied in many different arrangement and wherein two enclosures can be provided to produce quadraphonic effect.